Insects in the order Diptera include many familiar flying insects such as filth and biting flies and mosquitoes. Many species of Diptera are known as vectors for varieties of diseases in man, other animals, and plants. For example, diseases such as dysentery, cholera, and yaws may be transmitted on house flies' feet and mouthparts. Horse flies and deer flies are known to spread tularemia, loiasis, and trypanosomiasis. Black flies are known to spread human onchoceriasis and leucocytozoon infections of poultry. Sand flies are known to spread leishmaniasis. Mosquitoes are known to spread malaria, encephalitis, yellow fever, and filariasis. Accordingly, it is important to control flying or biting insects such as flies and mosquitoes, especially in less developed countries, to minimize and reduce the risk of these insects serving as vectors for diseases in humans.
Various chemicals and mixtures have been studied and used for insect repelling activities. For example, N,N-diethyl-m-toluamide (DEET), and dimethyl phthalate are widely used as insect repellents. DEET is very effective in protecting outdoor people from insects. Certain formulations containing DEET have been designed for cosmetic uses, for example, in sunscreen products such as lotions.
While DEET is an effective repellent, it is not particularly pleasing in smell, it stings when applied, and its use causes a number of harmful side effects in humans including injuries to eyes, mucous membranes, and sensitive skin. Because DEET is absorbed through the skin, toxic systemic reactions may result even when the compound is only used topically. Repeated exposure to DEET has been associated with incidences of seizures, irritability, confusion, insomnia, encephalopathy, and coma.
The potential hazards of using a product with DEET as an active ingredient indicate that there is a need for new methods for repelling insects.